US Undersecretary of State Nicholas Burns said the six powers, the five permament members of the UN Security Council plus Germany, were unified in their determination to halt Iran's uranium enrichment activities, which they fear are a cover for developing nuclear weapons.

But after weeks of lobbying by the United States, which wanted to impose swift sanctions against Tehran after it missed an August 31 UN deadline to halt its uranium enrichment, Burns said Tuesday that there was still no agreement on just when or how to impose the punitive measures.

The US, instead, has signed on to efforts by European Union foreign policy chief Javier Solana to pursue negotiations with the Iranians in hopes of convincing them to meet the UN demands.

"There was very strong support for Javier Solana's negotiations," Burns said.

He said if Solana succeeds in convincing the Iranians to verifiably suspend their enrichment program, US Secretary of State Condoleezza Rice would personally attend the launch of broader negotiations with Iran on improving relations with the Islamic state.

It would be the first direct negotiations between the two governments in 27 years.

But the six powers, meeting along with Italy, also agreed on a firm new deadline for obtaining an agreement with Iran, a senior US official said.

The official would not reveal the new deadline, but said it was "soon" and that the Iranians would be informed of the date.

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